//
// async_tcp_echo_server.cpp
// ~~~~~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2024 Christopher M. Kohlhoff (chris at kohlhoff dot com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//

#ifndef BOOST_ASIO_ENABLE_HANDLER_TRACKING
#define BOOST_ASIO_ENABLE_HANDLER_TRACKING
#endif

#include <boost/asio.hpp>
#include <cstdlib>
#include <iostream>
#include <memory>
#include <utility>

using boost::asio::ip::tcp;

// Define a helper macro to invoke BOOST_ASIO_HANDLER_LOCATION with the current
// file name, line number, and function name. For the function name, you might
// also consider using __PRETTY_FUNCTION__, BOOST_CURRENT_FUNCTION, or a hand-
// crafted name. For C++20 or later, you may also use std::source_location.
#define HANDLER_LOCATION                                                       \
  BOOST_ASIO_HANDLER_LOCATION((__FILE__, __LINE__, __func__))

class session : public std::enable_shared_from_this<session> {
public:
  session(tcp::socket socket) : socket_(std::move(socket)) {}

  void start() {
    HANDLER_LOCATION;

    do_read();
  }

private:
  void do_read() {
    HANDLER_LOCATION;

    auto self(shared_from_this());
    socket_.async_read_some(
        boost::asio::buffer(data_, max_length),
        [this, self](boost::system::error_code ec, std::size_t length) {
          HANDLER_LOCATION;

          if (!ec) {
            do_write(length);
          }
        });
  }

  void do_write(std::size_t length) {
    HANDLER_LOCATION;

    auto self(shared_from_this());
    boost::asio::async_write(
        socket_, boost::asio::buffer(data_, length),
        [this, self](boost::system::error_code ec, std::size_t /*length*/) {
          HANDLER_LOCATION;

          if (!ec) {
            do_read();
          }
        });
  }

  tcp::socket socket_;
  enum { max_length = 1024 };
  char data_[max_length];
};

class server {
public:
  server(boost::asio::io_context &io_context, short port)
      : acceptor_(io_context, tcp::endpoint(tcp::v4(), port)) {
    do_accept();
  }

private:
  void do_accept() {
    HANDLER_LOCATION;

    acceptor_.async_accept(
        [this](boost::system::error_code ec, tcp::socket socket) {
          HANDLER_LOCATION;

          if (!ec) {
            std::make_shared<session>(std::move(socket))->start();
          }

          do_accept();
        });
  }

  tcp::acceptor acceptor_;
};

int main(int argc, char *argv[]) {
  try {
    if (argc != 2) {
      std::cerr << "Usage: async_tcp_echo_server <port>\n";
      return 1;
    }

    boost::asio::io_context io_context;

    server s(io_context, std::atoi(argv[1]));

    io_context.run();
  } catch (std::exception &e) {
    std::cerr << "Exception: " << e.what() << "\n";
  }

  return 0;
}
